Conventional hemotoxicity testing, performed primarily during the preclinical phase of drug development, is based on parameters obtained from mature cells in peripheral blood or organ morphology and, as such, has little predictive value. The in vitro hematopoietic stem and progenitor cell colony-forming assays (CFA) provide validated and highly predictive procedures capable of improving efficacy and safety for new drugs. Although the CFAs were first introduced in 1966, they have never been used routinely, other than for research purposes, because they are time-consuming to perform, require considerable expertise and experience, are very costly and the results have to be manually enumerated, thereby not only suffering from lack of subjectivity, but also high throughput capability. Our Phase I application proposed a complete modification of the conventional CFAs such that the read-out would be a non-subjective fluorescence or luminescence signal and the test system would be robust, easy-to-use, cost-effective and have high throughput capability. This new CFA-based platform is called HALO (Hematopoietic/Hemotoxicity Assays via Luminescence Output). In the preliminary report included in this proposal, we show that HALO is (a) capable of detecting all primary hematopoietic lineages simultaneously, (b) has multispecies capability allowing human, nonhuman primate, rat, mouse and even dog hematopoietic cells to be detected side-by-side and (c) has multitasking capability so that cell proliferation and apoptosis/necrosis can be measure in the same assay. In addition, we have also used HALO in a specific application example to demonstrate the best time of day to administer the anti-cancer drugs, 5-fluorouracil and doxorubicin. In this Phase II application, we now propose 3 aims for refining the procedures to allow for automation, high throughput screening and validation. In Aim 1, we plan to fully optimize the 1st generation HALO for stem and lineage-specific progenitor cell populations from different animal species. This will be the basis for the 2 nd generation multitasking HALO platform. In Aim 2 we will develop off-the-shelf staging leading to a marketable HALO kit for research and later clinical purposes and automation capability so that the assay can be "ramped up" to accommodate for high-throughput testing. Finally in Aim 3, the HALO platform will undergo standardization and intralaboratory validation so that multitarget, multilineage and multispecies hemotoxicity comparisons can be performed on anti-cancer drugs. Commercialization of HALO has already begun and we expect the use of HALO by biotechnology and pharmaceutical companies to increase substantially in the immediate future thereby increasing our market share. In addition, we also expect the first HALO research kit to be available within the next 6-12 months. As far as we are aware, HALO is the first in vitro, cell-based, assay system that can be used at all stages of drug development, from screening to patient monitoring during clinical trials. With research and other clinical applications, the HALO platform will be a very unique and profitable product.